How much protein do you need to build muscle?

This has one of the cleanest answers in nutrition, because somebody went and found where the curve stops rising.

The number

That comes from a meta-analysis and meta-regression of resistance training studies, and the method matters: they used break-point analysis to find where the relationship between total protein intake and change in fat-free mass flattened.¹ It is not a round number somebody liked. It is where the data stopped responding.

The sports nutrition position stand recommends 1.4 to 2.0 g/kg a day for people training to build or keep muscle, which brackets that figure comfortably.² The two sources agree, arrived at differently.

How big the effect actually is

Worth stating plainly, because the number above is often quoted as though hitting it transforms things.

Across the same 49 trials, protein supplementation produced:

• 0.30 kg more fat-free mass
• 2.49 kg more on one-rep max strength

Over training periods of six weeks and longer.¹ Real, statistically clear, and modest. Protein is not what builds muscle. Training builds muscle, and protein removes a constraint on it.

That framing explains an otherwise confusing pair of findings from the same analysis:

• The effect shrank with increasing age.
• The effect was larger in people already resistance-trained.

Both make sense if protein is permissive. If your training is not driving adaptation, there is no constraint for protein to remove.

What the arithmetic looks like

The calculator does this from your weight and activity level, and shows which recommendation it used.

Two adjustments worth knowing. If you are carrying a lot of fat, scaling off total body weight overshoots, because fat tissue does not need feeding: an adjusted or lean body weight gives a more sensible figure. And if you are in a deficit, the higher end of the range is where the guidance points, which is a different situation with its own page.

Where the pound-per-pound rule came from

"One gram per pound of body weight" works out at roughly 2.2 g/kg, which sits above the point where gains stopped rising.

It is not dangerous. The Institute of Medicine set no tolerable upper intake level for protein, and the sports nutrition guidance describes intakes above its range as safe rather than as better.³² It is simply more protein than the evidence asks for, and it is expensive.

The rule survives because it is easy to remember in pounds. That is the whole reason.

What matters more than the number

Once you are somewhere between 1.4 and 1.8 g/kg, the protein question is answered and the remaining variables are elsewhere.

• Training that progresses. Adding load, repetitions or sets over months. Without this, protein has nothing to permit.
• Consistency over years. Muscle is built in units of months.
• Distribution across meals, which is a smaller effect than the daily total and a real one: how much protein per meal has the arithmetic.
• Enough total food. Building tissue in a large deficit is a harder problem than most people assume.

If you have your number and your training is not progressing, the number is not the thing to adjust.

Where this stops applying

These figures are for healthy adults training normally. If your kidney function is reduced, if you have liver disease, or if protein intake is already managed as part of your medical care, the target is set by your clinician and the ranges here are not aimed at you.